1. Field of the Invention
The present invention relates to a semiconductor substrate and to a method for its preparation. More particularly, the present invention relates to a silicon-on-sapphire (SOS) type semiconductor substrate and to a method for its preparation.
2. Description of the Prior Art
Because the small parasitic capacity of the silicon-on-sapphire structure enables the semiconductor device to increase its switching speed, studies concerning application of the silicon-on-sapphire type semiconductor device to practical uses are nowadays being actively developed. The conventional SOS type semiconductor substrate comprises base plate of a bulk sapphire and a crystalline silicon layer formed on the bulk sapphire base plate. However, this conventional SOS type semiconductor substrate has the following disadvantages.
1. The bulk sapphire is expensive. PA0 2. Since there is a mismatch between the crystal structure of the sapphire and the crystal structure of the silicon to be applied onto the sapphire, it is difficult to grow a good quality crystalline silicon film on the sapphire base plate.